Ultra High Sensitive Refractive Index Sensor Using a Metal Under-Clad Ridge Waveguide Modal Interferometer Near the Dispersion Turning Point

It is shown that by optimizing the core dimensions of a metal underclad ridge waveguide (MUCRW), a dispersion turning point (DTP) can be obtained in the dual mode region. The refractive index (RI) sensing characteristics of such a MUCRW modal interferometric sensor are examined around the DTP showing that extremely high RI sensitivity of ~90 μm/RIU and figure of merit ~4500 can be achieved for RI ~1.33. The adlayer sensitivity (~12 nm/nm) of the optimized structure is also found to be extremely high in the biologically relevant RI range which makes it a promising candidate for the bio-sensing applications. The effect of possible fabrication errors has been investigated and it is found that the considered structure provides robust sensing performance within these constraints.